An incoming Conservative government will repeal the Human Rights Act, Dominic Grieve promised his party conference last month. Sounds tough. But the reality is a little different.

As the shadow justice secretary explains, this controversial legislation would be replaced by a "British" Bill of Rights. But when? "I would like to think we could do it in the course of a parliament," Grieve tells me.

By my reckoning, it would take the best part of five years to bring new legislation into force. In the meantime, Labour's 1998 Act will remain law. Unlike Lord Irvine, who had a carefully crafted bill ready to launch as soon as Labour came to power in 1997, the Tories' Lord Chancellor-in-waiting is in no hurry.

Grieve is aiming for a consultation paper within a year of taking office, followed a year later by a draft bill. With time for pre-legislative scrutiny, parliamentary procedures and retraining for the judges, it would be 2015 before the changes took effect.

And what changes can we expect? Grieve suggests limiting administrative penalties and adding new rights such as trial by jury. But these pledges would be difficult to define and achieve. Administrative penalties, however unattractive, are cost-efficient. The right to jury trial is available in only a small minority of criminal cases, with important variations across the United Kingdom.

The best pledge that the Tories could come up with was to announce that a Conservative government would "free the police, probation and prison services to name offenders where necessary in order to protect the public and prevent crime".

But the authorities can do this already, as Grieve knows perfectly well. There was no need for him to announce that "a Conservative government will change the rules for people charged with protecting the public on the front line".

As he accepts, the belief that suspects' human rights are breached by police "wanted" posters is a myth. A pamphlet published at the conference by the campaign group Liberty cited a case from 2004 in which the Court of Appeal refused to ban leaflets identifying individuals against whom anti-social behaviour orders had been made.

But Grieve is too shrewd to be caught out that easily. He cites a little-known challenge to an Essex police sergeant who wanted to introduce an "offender naming scheme" in Brentwood. The High Court concluded in 2003 that more information would be needed — preferably from the Home Office — before it could decide whether the possible benefits of such a scheme were proportionate to the intrusion into an offender's privacy. Grieve regards that as a call for guidelines which the Home Office failed to provide.

More broadly, he makes it perfectly clear that Britain will not pull out of the European Convention on Human Rights. We will not be able to send people to countries where they will be tortured, he promises. Whatever else happens, individuals alleging breaches of their human rights will still be able to take the British government to the European Court in Strasbourg.

Does that mean that the convention will remain "incorporated" into domestic law to the extent that it is at present? Will judges still be required, as far as possible, to read legislation in a way that is compatible with the convention? "We have got to protect the rights which are enshrined in the convention," Grieve tells me at a Policy Exchange fringe meeting. "How we best do that is a subject on which we are still working."

He outlines several options. One would be a completely new text. Another would be to use the existing convention while "glossing" it with new interpretation clauses. "But we have to end up with something that is compatible, in broad terms, with the European Convention."

Grieve's view is that domestic law does not need to mirror the convention precisely. Indeed, the two can never be identical, because the national courts and Strasbourg may sometimes decide the same question in different ways. For example, in 2004 the law lords allowed the police to keep DNA samples taken from unconvicted suspects. Despite this, the Human Rights Court decided last year that the blanket retention of samples breached suspects' right to privacy.

It follows that on a topic such as privacy it would be possible for English law to strike a different balance between respect for private life and freedom of expression. In suggesting a rebalancing of these two rights, Grieve is right to say that parliament has always fought shy of legislating on privacy.

But judges would inevitably have the last word in individual cases. The real problem Grieve faces is rebalancing his long-standing commitment to human rights against the instincts of his political supporters.